1. Field of the Invention
The present invention relates generally to the field of solar energy utilization apparatus, and more particularly, to an automatic freeze protection system for use in solar energy collector systems.
2. Description of the Prior Art
Owing to the energy crisis, a great deal of research activity is presently being conducted throughout the world with respect to solar collectors for heating fluids for applications in the fields of water heating, space heating, air conditioning, etc., to thereby reduce the quantities of conventional fuels consumed. While numerous solar collectors may be found in the prior art, there is a continuing effort to produce collectors which have very high thermal efficiencies and yet which are relatively inexpensive to fabricate. The use of inexpensive materials, and the employment of labor saving techniques is of paramount importance in facilitating the widespread use of the collectors, and hence, in reducing the quantities of conventional fuel consumed.
The present invention is directed towards a problem which is encountered in cold weather climates. Specifically, in those areas wherein outside temperatures may drop near or below the freezing point of water, some form of protection must be provided to prevent water from freezing up within the collector or within the plumbing leading to and from the collector as its expansion by freezing can obviously cause very severe damage to the entire system.
One solution to this problem which has been suggested in the prior art is to add anti-freeze to the water in the collector. Anti-freeze, however, is not only expensive in and of itself, but is also poisonous and, accordingly, when used, necessitates the addition of costly safety equipment to ensure that the anti-freeze/water solution will not enter into the main water supply of the home of other building. For example, it is usually necessary to isolate the anti-freeze/water mixture from the main water supply by maintaining it in a closed loop system, and to then use the heated anti-freeze/water mixture to heat the main water supply through appropriate heat exchange means. This will not only raise the cost of the system, but will also lower its efficiency. Furthermore, notwithstanding the isolation of the anti-freeze/water mixture, there is always some danger that a certain amount of leakage into the main water supply could occur. For this reason, some states have forbidden its use in solar energy systems.
Yet a further disadvantage of such systems is the fact that, although the anti-freeze/water mixture will not freeze, it can drop to quite a low temperature during the night. Accordingly, when the sun comes up in the morning and begins heating the water, substantial time is needed to heat the cold fluid to a usable temperature, and this also results in a significant loss in efficiency.